State health officials have declared the flu to be widespread and prevalent in New York state.
The Department of Health says cases of the flu have been confirmed in 39 counties and in all five boroughs of New York City. Some 658 flu-related hospitalizations have been reported so far this flu season.
An average of 9,800 hospitalizations were reported in the last three flu seasons.
The declaration announced Wednesday means that health care workers who have not been vaccinated against the flu must wear masks when they're around patients.
Health Commissioner Howard Zucker says the flu vaccine remains the "best way" to avoid the virus.
Flu season typically runs from October through May.